add support for inline encryption to device mapper

This patch series adds support for inline encryption to the device mapper.

Patch 1 introduces the "passthrough" keyslot manager.

The regular keyslot manager is designed for inline encryption hardware that
have only a small fixed number of keyslots. A DM device itself does not
actually have only a small fixed number of keyslots - it doesn't actually
have any keyslots in the first place, and programming an encryption context
into a DM device doesn't make much semantic sense. It is possible for a DM
device to set up a keyslot manager with some "sufficiently large" number of
keyslots in its request queue, so that upper layers can use the inline
encryption capabilities of the DM device's underlying devices, but the
memory being allocated for the DM device's keyslots is a waste since they
won't actually be used by the DM device.

The passthrough keyslot manager solves this issue - when the block layer
sees that a request queue has a passthrough keyslot manager, it doesn't
attempt to program any encryption context into the keyslot manager. The
passthrough keyslot manager only allows the device to expose its inline
encryption capabilities, and a way for upper layers to evict keys if
necessary.

There also exist inline encryption hardware that can handle encryption
contexts directly, and allow users to pass them a data request along with
the encryption context (as opposed to inline encryption hardware that
require users to first program a keyslot with an encryption context, and
then require the users to pass the keyslot index with the data request).
Such devices can also make use of the passthrough keyslot manager.

Patch 2 introduces some keyslot manager functions useful for the device
mapper.

Patch 3 introduces the changes for inline encryption support for the device
mapper. A DM device only exposes the intersection of the crypto
capabilities of its underlying devices. This is so that in case a bio with
an encryption context is eventually mapped to an underlying device that
doesn't support that encryption context, the blk-crypto-fallback's cipher
tfms are allocated ahead of time by the call to blk_crypto_start_using_key.

Each DM target can now also specify the "DM_TARGET_PASSES_CRYPTO" flag in

84 more lines

The device mapper may map over devices that have inline encryption
capabilities, and to make use of those capabilities, the DM device must
itself advertise those inline encryption capabilities. One way to do this
would be to have the DM device set up a keyslot manager with a
"sufficiently large" number of keyslots, but that would use a lot of
memory. Also, the DM device itself has no "keyslots", and it doesn't make
much sense to talk about "programming a key into a DM device's keyslot
manager", so all that extra memory used to represent those keyslots is just
wasted. All a DM device really needs to be able to do is advertise the
crypto capabilities of the underlying devices in a coherent manner and
expose a way to evict keys from the underlying devices.

There are also devices with inline encryption hardware that do not
have a limited number of keyslots. One can send a raw encryption key along
with a bio to these devices (as opposed to typical inline encryption
hardware that require users to first program a raw encryption key into a
keyslot, and send the index of that keyslot along with the bio). These
devices also only need the same things from the keyslot manager that DM
devices need - a way to advertise crypto capabilities and potentially a way
to expose a function to evict keys from hardware.

So we introduce a "passthrough" keyslot manager that provides a way to
represent a keyslot manager that doesn't have just a limited number of
keyslots, and for which do not require keys to be programmed into keyslots.
DM devices can set up a passthrough keyslot manager in their request
queues, and advertise appropriate crypto capabilities based on those of the
underlying devices. Blk-crypto does not attempt to program keys into any
keyslots in the passthrough keyslot manager. Instead, if/when the bio is
resubmitted to the underlying device, blk-crypto will try to program the
key into the underlying device's keyslot manager.

Signed-off-by: Satya Tangirala <redacted>
Reviewed-by: Eric Biggers <redacted>
---
 block/keyslot-manager.c         | 39 +++++++++++++++++++++++++++++++++
 include/linux/keyslot-manager.h |  2 ++
 2 files changed, 41 insertions(+)

diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
index 86f8195d8039..ac7ce83a76e8 100644
--- a/block/keyslot-manager.c
+++ b/block/keyslot-manager.c

@@ -62,6 +62,11 @@ static inline void blk_ksm_hw_exit(struct blk_keyslot_manager *ksm)
 		pm_runtime_put_sync(ksm->dev);
 }
 
+static inline bool blk_ksm_is_passthrough(struct blk_keyslot_manager *ksm)
+{
+	return ksm->num_slots == 0;
+}
+
 /**
  * blk_ksm_init() - Initialize a keyslot manager
  * @ksm: The keyslot_manager to initialize.

@@ -205,6 +210,10 @@ blk_status_t blk_ksm_get_slot_for_key(struct blk_keyslot_manager *ksm,
 	int err;
 
 	*slot_ptr = NULL;
+
+	if (blk_ksm_is_passthrough(ksm))
+		return BLK_STS_OK;
+
 	down_read(&ksm->lock);
 	slot = blk_ksm_find_and_grab_keyslot(ksm, key);
 	up_read(&ksm->lock);

@@ -325,6 +334,16 @@ int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
 	struct blk_ksm_keyslot *slot;
 	int err = 0;
 
+	if (blk_ksm_is_passthrough(ksm)) {
+		if (ksm->ksm_ll_ops.keyslot_evict) {
+			blk_ksm_hw_enter(ksm);
+			err = ksm->ksm_ll_ops.keyslot_evict(ksm, key, -1);
+			blk_ksm_hw_exit(ksm);
+			return err;
+		}
+		return 0;
+	}
+
 	blk_ksm_hw_enter(ksm);
 	slot = blk_ksm_find_keyslot(ksm, key);
 	if (!slot)

@@ -360,6 +379,9 @@ void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm)
 {
 	unsigned int slot;
 
+	if (blk_ksm_is_passthrough(ksm))
+		return;
+
 	/* This is for device initialization, so don't resume the device */
 	down_write(&ksm->lock);
 	for (slot = 0; slot < ksm->num_slots; slot++) {

@@ -401,3 +423,20 @@ void blk_ksm_unregister(struct request_queue *q)
 {
 	q->ksm = NULL;
 }
+
+/**
+ * blk_ksm_init_passthrough() - Init a passthrough keyslot manager
+ * @ksm: The keyslot manager to init
+ *
+ * Initialize a passthrough keyslot manager.
+ * Called by e.g. storage drivers to set up a keyslot manager in their
+ * request_queue, when the storage driver wants to manage its keys by itself.
+ * This is useful for inline encryption hardware that doesn't have the concept
+ * of keyslots, and for layered devices.
+ */
+void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm)
+{
+	memset(ksm, 0, sizeof(*ksm));
+	init_rwsem(&ksm->lock);
+}
+EXPORT_SYMBOL_GPL(blk_ksm_init_passthrough);

diff --git a/include/linux/keyslot-manager.h b/include/linux/keyslot-manager.h
index 18f3f5346843..323e15dd6fa7 100644
--- a/include/linux/keyslot-manager.h
+++ b/include/linux/keyslot-manager.h

@@ -103,4 +103,6 @@ void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm);
 
 void blk_ksm_destroy(struct blk_keyslot_manager *ksm);
 
+void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm);
+
 #endif /* __LINUX_KEYSLOT_MANAGER_H */

-- 
2.30.0.365.g02bc693789-goog

Introduce blk_ksm_update_capabilities() to update the capabilities of
a keyslot manager (ksm) in-place. The pointer to a ksm in a device's
request queue may not be easily replaced, because upper layers like
the filesystem might access it (e.g. for programming keys/checking
capabilities) at the same time the device wants to replace that
request queue's ksm (and free the old ksm's memory). This function
allows the device to update the capabilities of the ksm in its request
queue directly. Devices can safely update the ksm this way without any
synchronization with upper layers *only* if the updated (new) ksm
continues to support all the crypto capabilities that the old ksm did
(see description below for blk_ksm_is_superset() for why this is so).

Also introduce blk_ksm_is_superset() which checks whether one ksm's
capabilities are a (not necessarily strict) superset of another ksm's.
The blk-crypto framework requires that crypto capabilities that were
advertised when a bio was created continue to be supported by the
device until that bio is ended - in practice this probably means that
a device's advertised crypto capabilities can *never* "shrink" (since
there's no synchronization between bio creation and when a device may
want to change its advertised capabilities) - so a previously
advertised crypto capability must always continue to be supported.
This function can be used to check that a new ksm is a valid
replacement for an old ksm.

Signed-off-by: Satya Tangirala <redacted>
---
 block/keyslot-manager.c         | 107 ++++++++++++++++++++++++++++++++
 include/linux/keyslot-manager.h |   9 +++
 2 files changed, 116 insertions(+)

diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
index ac7ce83a76e8..9f9494b80148 100644
--- a/block/keyslot-manager.c
+++ b/block/keyslot-manager.c

@@ -424,6 +424,113 @@ void blk_ksm_unregister(struct request_queue *q)
 	q->ksm = NULL;
 }
 
+/**
+ * blk_ksm_intersect_modes() - restrict supported modes by child device
+ * @parent: The keyslot manager for parent device
+ * @child: The keyslot manager for child device, or NULL
+ *
+ * Clear any crypto mode support bits in @parent that aren't set in @child.
+ * If @child is NULL, then all parent bits are cleared.
+ *
+ * Only use this when setting up the keyslot manager for a layered device,
+ * before it's been exposed yet.
+ */
+void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
+			     const struct blk_keyslot_manager *child)
+{
+	if (child) {
+		unsigned int i;
+
+		parent->max_dun_bytes_supported =
+			min(parent->max_dun_bytes_supported,
+			    child->max_dun_bytes_supported);
+		for (i = 0; i < ARRAY_SIZE(child->crypto_modes_supported);
+		     i++) {
+			parent->crypto_modes_supported[i] &=
+				child->crypto_modes_supported[i];
+		}
+	} else {
+		parent->max_dun_bytes_supported = 0;
+		memset(parent->crypto_modes_supported, 0,
+		       sizeof(parent->crypto_modes_supported));
+	}
+}
+EXPORT_SYMBOL_GPL(blk_ksm_intersect_modes);
+
+/**
+ * blk_ksm_is_superset() - Check if a KSM supports a superset of crypto modes
+ *			   and DUN bytes that another KSM supports. Here,
+ *			   "superset" refers to the mathematical meaning of the
+ *			   word - i.e. if two KSMs have the *same* capabilities,
+ *			   they *are* considered supersets of each other.
+ * @ksm_superset: The KSM that we want to verify is a superset
+ * @ksm_subset: The KSM that we want to verify is a subset
+ *
+ * Return: True if @ksm_superset supports a superset of the crypto modes and DUN
+ *	   bytes that @ksm_subset supports.
+ */
+bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
+			 struct blk_keyslot_manager *ksm_subset)
+{
+	int i;
+
+	if (!ksm_subset)
+		return true;
+
+	if (!ksm_superset)
+		return false;
+
+	for (i = 0; i < ARRAY_SIZE(ksm_superset->crypto_modes_supported); i++) {
+		if (ksm_subset->crypto_modes_supported[i] &
+		    (~ksm_superset->crypto_modes_supported[i])) {
+			return false;
+		}
+	}
+
+	if (ksm_subset->max_dun_bytes_supported >
+	    ksm_superset->max_dun_bytes_supported) {
+		return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(blk_ksm_is_superset);
+
+/**
+ * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
+ *				   another KSM
+ * @target_ksm: The KSM whose restrictions to update.
+ * @reference_ksm: The KSM to whose restrictions this function will update
+ *		   @target_ksm's restrictions to.
+ *
+ * Blk-crypto requires that crypto capabilities that were
+ * advertised when a bio was created continue to be supported by the
+ * device until that bio is ended. This is turn means that a device cannot
+ * shrink its advertised crypto capabilities without any explicit
+ * synchronization with upper layers. So if there's no such explicit
+ * synchronization, @reference_ksm must support all the crypto capabilities that
+ * @target_ksm does
+ * (i.e. we need blk_ksm_is_superset(@reference_ksm, @target_ksm) == true).
+ *
+ * Note also that as long as the crypto capabilities are being expanded, the
+ * order of updates becoming visible is not important because it's alright
+ * for blk-crypto to see stale values - they only cause blk-crypto to
+ * believe that a crypto capability isn't supported when it actually is (which
+ * might result in blk-crypto-fallback being used if available, or the bio being
+ * failed).
+ */
+void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
+				 struct blk_keyslot_manager *reference_ksm)
+{
+	memcpy(target_ksm->crypto_modes_supported,
+	       reference_ksm->crypto_modes_supported,
+	       sizeof(target_ksm->crypto_modes_supported));
+
+	target_ksm->max_dun_bytes_supported =
+				reference_ksm->max_dun_bytes_supported;
+}
+EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
+
 /**
  * blk_ksm_init_passthrough() - Init a passthrough keyslot manager
  * @ksm: The keyslot manager to init

diff --git a/include/linux/keyslot-manager.h b/include/linux/keyslot-manager.h
index 323e15dd6fa7..164568f52be7 100644
--- a/include/linux/keyslot-manager.h
+++ b/include/linux/keyslot-manager.h

@@ -103,6 +103,15 @@ void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm);
 
 void blk_ksm_destroy(struct blk_keyslot_manager *ksm);
 
+void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
+			     const struct blk_keyslot_manager *child);
+
 void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm);
 
+bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
+			 struct blk_keyslot_manager *ksm_subset);
+
+void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
+				 struct blk_keyslot_manager *reference_ksm);
+
 #endif /* __LINUX_KEYSLOT_MANAGER_H */

-- 
2.30.0.365.g02bc693789-goog

Update the device-mapper core to support exposing the inline crypto
support of the underlying device(s) through the device-mapper device.

This works by creating a "passthrough keyslot manager" for the dm
device, which declares support for encryption settings which all
underlying devices support.  When a supported setting is used, the bio
cloning code handles cloning the crypto context to the bios for all the
underlying devices.  When an unsupported setting is used, the blk-crypto
fallback is used as usual.

Crypto support on each underlying device is ignored unless the
corresponding dm target opts into exposing it.  This is needed because
for inline crypto to semantically operate on the original bio, the data
must not be transformed by the dm target.  Thus, targets like dm-linear
can expose crypto support of the underlying device, but targets like
dm-crypt can't.  (dm-crypt could use inline crypto itself, though.)

A DM device's table can only be changed if the "new" inline encryption
capabilities are a (*not* necessarily strict) superset of the "old" inline
encryption capabilities.  Attempts to make changes to the table that result
in some inline encryption capability becoming no longer supported will be
rejected.

For the sake of clarity, key eviction from underlying devices will be
handled in a future patch.

Co-developed-by: Eric Biggers <redacted>
Signed-off-by: Eric Biggers <redacted>
Signed-off-by: Satya Tangirala <redacted>
---
 drivers/md/dm-core.h          |   5 ++
 drivers/md/dm-table.c         | 157 ++++++++++++++++++++++++++++++++++
 drivers/md/dm.c               |  18 +++-
 include/linux/device-mapper.h |  11 +++
 4 files changed, 190 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 086d293c2b03..bf3e66f39a4a 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h

@@ -13,6 +13,7 @@
 #include <linux/ktime.h>
 #include <linux/genhd.h>
 #include <linux/blk-mq.h>
+#include <linux/keyslot-manager.h>
 
 #include <trace/events/block.h>
 

@@ -162,6 +163,10 @@ struct dm_table {
 	void *event_context;
 
 	struct dm_md_mempools *mempools;
+
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+	struct blk_keyslot_manager *ksm;
+#endif
 };
 
 static inline struct completion *dm_get_completion_from_kobject(struct kobject *kobj)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 4acf2342f7ad..b37f69343923 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c

@@ -187,6 +187,8 @@ static void free_devices(struct list_head *devices, struct mapped_device *md)
 	}
 }
 
+static void dm_table_destroy_keyslot_manager(struct dm_table *t);
+
 void dm_table_destroy(struct dm_table *t)
 {
 	unsigned int i;

@@ -215,6 +217,8 @@ void dm_table_destroy(struct dm_table *t)
 
 	dm_free_md_mempools(t->mempools);
 
+	dm_table_destroy_keyslot_manager(t);
+
 	kfree(t);
 }
 

@@ -1203,6 +1207,152 @@ static int dm_table_register_integrity(struct dm_table *t)
 	return 0;
 }
 
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+
+struct dm_keyslot_manager {
+	struct blk_keyslot_manager ksm;
+	struct mapped_device *md;
+};
+
+static int device_intersect_crypto_modes(struct dm_target *ti,
+					 struct dm_dev *dev, sector_t start,
+					 sector_t len, void *data)
+{
+	struct blk_keyslot_manager *parent = data;
+	struct blk_keyslot_manager *child = bdev_get_queue(dev->bdev)->ksm;
+
+	blk_ksm_intersect_modes(parent, child);
+	return 0;
+}
+
+void dm_destroy_keyslot_manager(struct blk_keyslot_manager *ksm)
+{
+	struct dm_keyslot_manager *dksm = container_of(ksm,
+						       struct dm_keyslot_manager,
+						       ksm);
+
+	if (!ksm)
+		return;
+
+	blk_ksm_destroy(ksm);
+	kfree(dksm);
+}
+
+static void dm_table_destroy_keyslot_manager(struct dm_table *t)
+{
+	dm_destroy_keyslot_manager(t->ksm);
+	t->ksm = NULL;
+}
+
+/*
+ * Constructs and returns a keyslot manager that represents the crypto
+ * capabilities of the devices described by the dm_table. However, if the
+ * constructed keyslot manager does not support a superset of the crypto
+ * capabilities supported by the current keyslot manager of the mapped_device,
+ * it returns an error instead, since we don't support restricting crypto
+ * capabilities on table changes. Finally, if the constructed keyslot manager
+ * doesn't actually support any crypto modes at all, it just returns NULL.
+ */
+static int
+dm_table_construct_keyslot_manager(struct dm_table *t)
+{
+	struct dm_keyslot_manager *dksm;
+	struct blk_keyslot_manager *ksm;
+	struct dm_target *ti;
+	unsigned int i;
+	bool ksm_is_empty = true;
+
+	dksm = kmalloc(sizeof(*dksm), GFP_KERNEL);
+	if (!dksm)
+		return -ENOMEM;
+	dksm->md = t->md;
+
+	ksm = &dksm->ksm;
+	blk_ksm_init_passthrough(ksm);
+	ksm->max_dun_bytes_supported = UINT_MAX;
+	memset(ksm->crypto_modes_supported, 0xFF,
+	       sizeof(ksm->crypto_modes_supported));
+
+	for (i = 0; i < dm_table_get_num_targets(t); i++) {
+		ti = dm_table_get_target(t, i);
+
+		if (!dm_target_passes_crypto(ti->type)) {
+			blk_ksm_intersect_modes(ksm, NULL);
+			break;
+		}
+		if (!ti->type->iterate_devices)
+			continue;
+		ti->type->iterate_devices(ti, device_intersect_crypto_modes,
+					  ksm);
+	}
+
+	if (t->md->queue && !blk_ksm_is_superset(ksm, t->md->queue->ksm)) {
+		DMWARN("Inline encryption capabilities of new DM table were more restrictive than the old table's. This is not supported!");
+		dm_destroy_keyslot_manager(ksm);
+		return -EINVAL;
+	}
+
+	/*
+	 * If the new KSM doesn't actually support any crypto modes, we may as
+	 * well represent it with a NULL ksm.
+	 */
+	ksm_is_empty = true;
+	for (i = 0; i < ARRAY_SIZE(ksm->crypto_modes_supported); i++) {
+		if (ksm->crypto_modes_supported[i]) {
+			ksm_is_empty = false;
+			break;
+		}
+	}
+
+	if (ksm_is_empty) {
+		dm_destroy_keyslot_manager(ksm);
+		ksm = NULL;
+	}
+
+	t->ksm = ksm;
+
+	return 0;
+}
+
+static void dm_update_keyslot_manager(struct request_queue *q,
+				      struct dm_table *t)
+{
+	if (!t->ksm)
+		return;
+
+	/* Make the ksm less restrictive */
+	if (!q->ksm) {
+		blk_ksm_register(t->ksm, q);
+	} else {
+		blk_ksm_update_capabilities(q->ksm, t->ksm);
+		dm_destroy_keyslot_manager(t->ksm);
+	}
+	t->ksm = NULL;
+}
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static int
+dm_table_construct_keyslot_manager(struct dm_table *t)
+{
+	return 0;
+}
+
+void dm_destroy_keyslot_manager(struct blk_keyslot_manager *ksm)
+{
+}
+
+static void dm_table_destroy_keyslot_manager(struct dm_table *t)
+{
+}
+
+static void dm_update_keyslot_manager(struct request_queue *q,
+				      struct dm_table *t)
+{
+}
+
+#endif /* !CONFIG_BLK_INLINE_ENCRYPTION */
+
 /*
  * Prepares the table for use by building the indices,
  * setting the type, and allocating mempools.

@@ -1229,6 +1379,12 @@ int dm_table_complete(struct dm_table *t)
 		return r;
 	}
 
+	r = dm_table_construct_keyslot_manager(t);
+	if (r) {
+		DMERR("could not construct keyslot manager.");
+		return r;
+	}
+
 	r = dm_table_alloc_md_mempools(t, t->md);
 	if (r)
 		DMERR("unable to allocate mempools");

@@ -1891,6 +2047,7 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	}
 #endif
 
+	dm_update_keyslot_manager(q, t);
 	blk_queue_update_readahead(q);
 }
 

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7bac564f3faa..ee0434764941 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c

@@ -28,6 +28,7 @@
 #include <linux/refcount.h>
 #include <linux/part_stat.h>
 #include <linux/blk-crypto.h>
+#include <linux/keyslot-manager.h>
 
 #define DM_MSG_PREFIX "core"
 

@@ -1718,6 +1719,19 @@ static const struct dax_operations dm_dax_ops;
 
 static void dm_wq_work(struct work_struct *work);
 
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+static void dm_queue_destroy_keyslot_manager(struct request_queue *q)
+{
+	dm_destroy_keyslot_manager(q->ksm);
+}
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline void dm_queue_destroy_keyslot_manager(struct request_queue *q)
+{
+}
+#endif /* !CONFIG_BLK_INLINE_ENCRYPTION */
+
 static void cleanup_mapped_device(struct mapped_device *md)
 {
 	if (md->wq)

@@ -1739,8 +1753,10 @@ static void cleanup_mapped_device(struct mapped_device *md)
 		put_disk(md->disk);
 	}
 
-	if (md->queue)
+	if (md->queue) {
+		dm_queue_destroy_keyslot_manager(md->queue);
 		blk_cleanup_queue(md->queue);
+	}
 
 	cleanup_srcu_struct(&md->io_barrier);
 

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 61a66fb8ebb3..d2142f5a82a7 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h

@@ -257,6 +257,12 @@ struct target_type {
 #define DM_TARGET_NOWAIT		0x00000080
 #define dm_target_supports_nowait(type) ((type)->features & DM_TARGET_NOWAIT)
 
+/*
+ *
+ */
+#define DM_TARGET_PASSES_CRYPTO		0x00000100
+#define dm_target_passes_crypto(type) ((type)->features & DM_TARGET_PASSES_CRYPTO)
+
 struct dm_target {
 	struct dm_table *table;
 	struct target_type *type;

@@ -533,6 +539,11 @@ void dm_table_run_md_queue_async(struct dm_table *t);
 struct dm_table *dm_swap_table(struct mapped_device *md,
 			       struct dm_table *t);
 
+/*
+ * Table keyslot manager functions
+ */
+void dm_destroy_keyslot_manager(struct blk_keyslot_manager *ksm);
+
 /*
  * A wrapper around vmalloc.
  */

-- 
2.30.0.365.g02bc693789-goog

dm-linear and dm-flakey obviously can pass through inline crypto support.

Co-developed-by: Eric Biggers <redacted>
Signed-off-by: Eric Biggers <redacted>
Signed-off-by: Satya Tangirala <redacted>
---
 drivers/md/dm-flakey.c | 4 +++-
 drivers/md/dm-linear.c | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index a2cc9e45cbba..30c6bc151213 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c

@@ -482,8 +482,10 @@ static struct target_type flakey_target = {
 	.name   = "flakey",
 	.version = {1, 5, 0},
 #ifdef CONFIG_BLK_DEV_ZONED
-	.features = DM_TARGET_ZONED_HM,
+	.features = DM_TARGET_ZONED_HM | DM_TARGET_PASSES_CRYPTO,
 	.report_zones = flakey_report_zones,
+#else
+	.features = DM_TARGET_PASSES_CRYPTO,
 #endif
 	.module = THIS_MODULE,
 	.ctr    = flakey_ctr,

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 00774b5d7668..fc9c4272c10d 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c

@@ -229,10 +229,11 @@ static struct target_type linear_target = {
 	.version = {1, 4, 0},
 #ifdef CONFIG_BLK_DEV_ZONED
 	.features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_NOWAIT |
-		    DM_TARGET_ZONED_HM,
+		    DM_TARGET_ZONED_HM | DM_TARGET_PASSES_CRYPTO,
 	.report_zones = linear_report_zones,
 #else
-	.features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_NOWAIT,
+	.features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_NOWAIT |
+		    DM_TARGET_PASSES_CRYPTO,
 #endif
 	.module = THIS_MODULE,
 	.ctr    = linear_ctr,

-- 
2.30.0.365.g02bc693789-goog

Now that device mapper supports inline encryption, add the ability to
evict keys from all underlying devices. When an upper layer requests
a key eviction, we simply iterate through all underlying devices
and evict that key from each device.

Co-developed-by: Eric Biggers <redacted>
Signed-off-by: Eric Biggers <redacted>
Signed-off-by: Satya Tangirala <redacted>
---
 block/blk-crypto.c    |  1 +
 drivers/md/dm-table.c | 53 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index 5da43f0973b4..c2be8f15006c 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c

@@ -409,3 +409,4 @@ int blk_crypto_evict_key(struct request_queue *q,
 	 */
 	return blk_crypto_fallback_evict_key(key);
 }
+EXPORT_SYMBOL_GPL(blk_crypto_evict_key);

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index b37f69343923..3eacc5329603 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c

@@ -1214,6 +1214,58 @@ struct dm_keyslot_manager {
 	struct mapped_device *md;
 };
 
+struct dm_keyslot_evict_args {
+	const struct blk_crypto_key *key;
+	int err;
+};
+
+static int dm_keyslot_evict_callback(struct dm_target *ti, struct dm_dev *dev,
+				     sector_t start, sector_t len, void *data)
+{
+	struct dm_keyslot_evict_args *args = data;
+	int err;
+
+	err = blk_crypto_evict_key(bdev_get_queue(dev->bdev), args->key);
+	if (!args->err)
+		args->err = err;
+	/* Always try to evict the key from all devices. */
+	return 0;
+}
+
+/*
+ * When an inline encryption key is evicted from a device-mapper device, evict
+ * it from all the underlying devices.
+ */
+static int dm_keyslot_evict(struct blk_keyslot_manager *ksm,
+			    const struct blk_crypto_key *key, unsigned int slot)
+{
+	struct dm_keyslot_manager *dksm = container_of(ksm,
+						       struct dm_keyslot_manager,
+						       ksm);
+	struct mapped_device *md = dksm->md;
+	struct dm_keyslot_evict_args args = { key };
+	struct dm_table *t;
+	int srcu_idx;
+	int i;
+	struct dm_target *ti;
+
+	t = dm_get_live_table(md, &srcu_idx);
+	if (!t)
+		return 0;
+	for (i = 0; i < dm_table_get_num_targets(t); i++) {
+		ti = dm_table_get_target(t, i);
+		if (!ti->type->iterate_devices)
+			continue;
+		ti->type->iterate_devices(ti, dm_keyslot_evict_callback, &args);
+	}
+	dm_put_live_table(md, srcu_idx);
+	return args.err;
+}
+
+static struct blk_ksm_ll_ops dm_ksm_ll_ops = {
+	.keyslot_evict = dm_keyslot_evict,
+};
+
 static int device_intersect_crypto_modes(struct dm_target *ti,
 					 struct dm_dev *dev, sector_t start,
 					 sector_t len, void *data)

@@ -1269,6 +1321,7 @@ dm_table_construct_keyslot_manager(struct dm_table *t)
 
 	ksm = &dksm->ksm;
 	blk_ksm_init_passthrough(ksm);
+	ksm->ksm_ll_ops = dm_ksm_ll_ops;
 	ksm->max_dun_bytes_supported = UINT_MAX;
 	memset(ksm->crypto_modes_supported, 0xFF,
 	       sizeof(ksm->crypto_modes_supported));

-- 
2.30.0.365.g02bc693789-goog

On Mon, Feb 01 2021 at 12:10am -0500,
Satya Tangirala [off-list ref] wrote:

This patch series adds support for inline encryption to the device mapper.

Patch 1 introduces the "passthrough" keyslot manager.

The regular keyslot manager is designed for inline encryption hardware that
have only a small fixed number of keyslots. A DM device itself does not
actually have only a small fixed number of keyslots - it doesn't actually
have any keyslots in the first place, and programming an encryption context
into a DM device doesn't make much semantic sense. It is possible for a DM
device to set up a keyslot manager with some "sufficiently large" number of
keyslots in its request queue, so that upper layers can use the inline
encryption capabilities of the DM device's underlying devices, but the
memory being allocated for the DM device's keyslots is a waste since they
won't actually be used by the DM device.

The passthrough keyslot manager solves this issue - when the block layer
sees that a request queue has a passthrough keyslot manager, it doesn't
attempt to program any encryption context into the keyslot manager. The
passthrough keyslot manager only allows the device to expose its inline
encryption capabilities, and a way for upper layers to evict keys if
necessary.

There also exist inline encryption hardware that can handle encryption
contexts directly, and allow users to pass them a data request along with
the encryption context (as opposed to inline encryption hardware that
require users to first program a keyslot with an encryption context, and
then require the users to pass the keyslot index with the data request).
Such devices can also make use of the passthrough keyslot manager.

Patch 2 introduces some keyslot manager functions useful for the device
mapper.

Patch 3 introduces the changes for inline encryption support for the device
mapper. A DM device only exposes the intersection of the crypto
capabilities of its underlying devices. This is so that in case a bio with
an encryption context is eventually mapped to an underlying device that
doesn't support that encryption context, the blk-crypto-fallback's cipher
tfms are allocated ahead of time by the call to blk_crypto_start_using_key.

Each DM target can now also specify the "DM_TARGET_PASSES_CRYPTO" flag in

84 more quoted lines

This set looks good to me now.

To avoid DM needing another rebase on block: Jens (and others), would
you like to review patches 1 and 2 (and reply with your Reviewed-by) so
I could pickup the DM required keyslot-manager changes along with
patches 3-5?

Thanks,
Mike

On Mon, Feb 01, 2021 at 05:10:16AM +0000, Satya Tangirala wrote:

Introduce blk_ksm_update_capabilities() to update the capabilities of
a keyslot manager (ksm) in-place. The pointer to a ksm in a device's
request queue may not be easily replaced, because upper layers like
the filesystem might access it (e.g. for programming keys/checking
capabilities) at the same time the device wants to replace that
request queue's ksm (and free the old ksm's memory). This function
allows the device to update the capabilities of the ksm in its request
queue directly. Devices can safely update the ksm this way without any
synchronization with upper layers *only* if the updated (new) ksm
continues to support all the crypto capabilities that the old ksm did
(see description below for blk_ksm_is_superset() for why this is so).

Also introduce blk_ksm_is_superset() which checks whether one ksm's
capabilities are a (not necessarily strict) superset of another ksm's.
The blk-crypto framework requires that crypto capabilities that were
advertised when a bio was created continue to be supported by the
device until that bio is ended - in practice this probably means that
a device's advertised crypto capabilities can *never* "shrink" (since
there's no synchronization between bio creation and when a device may
want to change its advertised capabilities) - so a previously
advertised crypto capability must always continue to be supported.
This function can be used to check that a new ksm is a valid
replacement for an old ksm.

Signed-off-by: Satya Tangirala <redacted>

Looks good, you can add:

Reviewed-by: Eric Biggers <redacted>

On 2/10/21 12:33 PM, Mike Snitzer wrote:

On Mon, Feb 01 2021 at 12:10am -0500,
Satya Tangirala [off-list ref] wrote:

quoted

This patch series adds support for inline encryption to the device mapper.

Patch 1 introduces the "passthrough" keyslot manager.

The regular keyslot manager is designed for inline encryption hardware that
have only a small fixed number of keyslots. A DM device itself does not
actually have only a small fixed number of keyslots - it doesn't actually
have any keyslots in the first place, and programming an encryption context
into a DM device doesn't make much semantic sense. It is possible for a DM
device to set up a keyslot manager with some "sufficiently large" number of
keyslots in its request queue, so that upper layers can use the inline
encryption capabilities of the DM device's underlying devices, but the
memory being allocated for the DM device's keyslots is a waste since they
won't actually be used by the DM device.

The passthrough keyslot manager solves this issue - when the block layer
sees that a request queue has a passthrough keyslot manager, it doesn't
attempt to program any encryption context into the keyslot manager. The
passthrough keyslot manager only allows the device to expose its inline
encryption capabilities, and a way for upper layers to evict keys if
necessary.

There also exist inline encryption hardware that can handle encryption
contexts directly, and allow users to pass them a data request along with
the encryption context (as opposed to inline encryption hardware that
require users to first program a keyslot with an encryption context, and
then require the users to pass the keyslot index with the data request).
Such devices can also make use of the passthrough keyslot manager.

Patch 2 introduces some keyslot manager functions useful for the device
mapper.

Patch 3 introduces the changes for inline encryption support for the device
mapper. A DM device only exposes the intersection of the crypto
capabilities of its underlying devices. This is so that in case a bio with
an encryption context is eventually mapped to an underlying device that
doesn't support that encryption context, the blk-crypto-fallback's cipher

94 more quoted lines

You can add my acked-by to 1+2 and queue it up.

-- 
Jens Axboe

On Mon, Feb 01, 2021 at 05:10:17AM +0000, Satya Tangirala wrote:

Update the device-mapper core to support exposing the inline crypto
support of the underlying device(s) through the device-mapper device.

This works by creating a "passthrough keyslot manager" for the dm
device, which declares support for encryption settings which all
underlying devices support.  When a supported setting is used, the bio
cloning code handles cloning the crypto context to the bios for all the
underlying devices.  When an unsupported setting is used, the blk-crypto
fallback is used as usual.

Crypto support on each underlying device is ignored unless the
corresponding dm target opts into exposing it.  This is needed because
for inline crypto to semantically operate on the original bio, the data
must not be transformed by the dm target.  Thus, targets like dm-linear
can expose crypto support of the underlying device, but targets like
dm-crypt can't.  (dm-crypt could use inline crypto itself, though.)

A DM device's table can only be changed if the "new" inline encryption
capabilities are a (*not* necessarily strict) superset of the "old" inline
encryption capabilities.  Attempts to make changes to the table that result
in some inline encryption capability becoming no longer supported will be
rejected.

For the sake of clarity, key eviction from underlying devices will be
handled in a future patch.

Co-developed-by: Eric Biggers <redacted>
Signed-off-by: Eric Biggers <redacted>
Signed-off-by: Satya Tangirala <redacted>

I don't see any obvious issues with this latest version.  I assume you've tested
it on real hardware?

If it's needed despite my Co-developed-by, feel free to add:

Reviewed-by: Eric Biggers <redacted>

A few nits about comments, in case you resend:

It might be helpful if there was a brief comment here that explained that this
field is only set temporarily while the table is being set up, and it gets set
to NULL after the capabilities have been transferred to the request_queue.
I.e., it's not something that stays around here while the dm device is active.

This doesn't "return" the keyslot manager anymore, but rather assigns it to
t->ksm.  It would also be helpful if the comment explicitly mentioned that the
goal is to find the capabilities that all the devices have in common.

E.g. "Initializes t->ksm with a keyslot manager that represents the common set
of crypto capabilities of the devices described by the dm_table.".

The above comment isn't very useful :-)

- Eric

On Mon, Feb 01, 2021 at 05:10:18AM +0000, Satya Tangirala wrote:

Now that device mapper supports inline encryption, add the ability to
evict keys from all underlying devices. When an upper layer requests
a key eviction, we simply iterate through all underlying devices
and evict that key from each device.

Co-developed-by: Eric Biggers <redacted>
Signed-off-by: Eric Biggers <redacted>
Signed-off-by: Satya Tangirala <redacted>

This latest version looks good to me.  If it's needed despite my
Co-developed-by, feel free to add:

	Reviewed-by: Eric Biggers [off-list ref]

- Eric

On Mon, Feb 01, 2021 at 05:10:19AM +0000, Satya Tangirala wrote:

5 more quoted lines

This latest version looks good to me.  If it's needed despite my
Co-developed-by, feel free to add:

	Reviewed-by: Eric Biggers [off-list ref]

BTW, the #ifdef for CONFIG_BLK_DEV_ZONED is error-prone (though it's a
pre-existing issue).  I wonder if DM_TARGET_ZONED_HM should be defined to 0 when
!CONFIG_BLK_DEV_ZONED, which would avoid the need for the #ifdef on .features.

- Eric

On Wed, Feb 10, 2021 at 12:17:30PM -0800, Eric Biggers wrote:

On Mon, Feb 01, 2021 at 05:10:17AM +0000, Satya Tangirala wrote:

quoted

Update the device-mapper core to support exposing the inline crypto
support of the underlying device(s) through the device-mapper device.

This works by creating a "passthrough keyslot manager" for the dm
device, which declares support for encryption settings which all
underlying devices support.  When a supported setting is used, the bio
cloning code handles cloning the crypto context to the bios for all the
underlying devices.  When an unsupported setting is used, the blk-crypto
fallback is used as usual.

Crypto support on each underlying device is ignored unless the
corresponding dm target opts into exposing it.  This is needed because
for inline crypto to semantically operate on the original bio, the data
must not be transformed by the dm target.  Thus, targets like dm-linear
can expose crypto support of the underlying device, but targets like
dm-crypt can't.  (dm-crypt could use inline crypto itself, though.)

A DM device's table can only be changed if the "new" inline encryption
capabilities are a (*not* necessarily strict) superset of the "old" inline
encryption capabilities.  Attempts to make changes to the table that result
in some inline encryption capability becoming no longer supported will be
rejected.

For the sake of clarity, key eviction from underlying devices will be
handled in a future patch.

Co-developed-by: Eric Biggers <redacted>
Signed-off-by: Eric Biggers <redacted>
Signed-off-by: Satya Tangirala <redacted>

I don't see any obvious issues with this latest version.  I assume you've tested
it on real hardware?

If it's needed despite my Co-developed-by, feel free to add:

Reviewed-by: Eric Biggers <redacted>

A few nits about comments, in case you resend:

Thanks! I addressed the nits, added acked/reviewed-bys and resent v5.

On Wed, Feb 10, 2021 at 12:59:59PM -0700, Jens Axboe wrote:

On 2/10/21 12:33 PM, Mike Snitzer wrote:

quoted

On Mon, Feb 01 2021 at 12:10am -0500,
Satya Tangirala [off-list ref] wrote:

quoted

This patch series adds support for inline encryption to the device mapper.

Patch 1 introduces the "passthrough" keyslot manager.

The regular keyslot manager is designed for inline encryption hardware that
have only a small fixed number of keyslots. A DM device itself does not
actually have only a small fixed number of keyslots - it doesn't actually
have any keyslots in the first place, and programming an encryption context
into a DM device doesn't make much semantic sense. It is possible for a DM
device to set up a keyslot manager with some "sufficiently large" number of
keyslots in its request queue, so that upper layers can use the inline
encryption capabilities of the DM device's underlying devices, but the
memory being allocated for the DM device's keyslots is a waste since they
won't actually be used by the DM device.

The passthrough keyslot manager solves this issue - when the block layer
sees that a request queue has a passthrough keyslot manager, it doesn't
attempt to program any encryption context into the keyslot manager. The
passthrough keyslot manager only allows the device to expose its inline
encryption capabilities, and a way for upper layers to evict keys if
necessary.

There also exist inline encryption hardware that can handle encryption
contexts directly, and allow users to pass them a data request along with
the encryption context (as opposed to inline encryption hardware that
require users to first program a keyslot with an encryption context, and
then require the users to pass the keyslot index with the data request).
Such devices can also make use of the passthrough keyslot manager.

Patch 2 introduces some keyslot manager functions useful for the device
mapper.

Patch 3 introduces the changes for inline encryption support for the device
mapper. A DM device only exposes the intersection of the crypto
capabilities of its underlying devices. This is so that in case a bio with
an encryption context is eventually mapped to an underlying device that

98 more quoted lines

I resent the series (as v5) while addressing the comments Eric had on
Patch 3 (the changes were only to comments, so no functional
changes). I also added the acked/reviewed-bys.

-- 
Jens Axboe

On Thu, Feb 11 2021 at  6:01pm -0500,
Satya Tangirala [off-list ref] wrote:

On Wed, Feb 10, 2021 at 12:59:59PM -0700, Jens Axboe wrote:

quoted

On 2/10/21 12:33 PM, Mike Snitzer wrote:

quoted

On Mon, Feb 01 2021 at 12:10am -0500,
Satya Tangirala [off-list ref] wrote:

quoted

This patch series adds support for inline encryption to the device mapper.

Patch 1 introduces the "passthrough" keyslot manager.

The regular keyslot manager is designed for inline encryption hardware that
have only a small fixed number of keyslots. A DM device itself does not
actually have only a small fixed number of keyslots - it doesn't actually
have any keyslots in the first place, and programming an encryption context
into a DM device doesn't make much semantic sense. It is possible for a DM
device to set up a keyslot manager with some "sufficiently large" number of
keyslots in its request queue, so that upper layers can use the inline
encryption capabilities of the DM device's underlying devices, but the
memory being allocated for the DM device's keyslots is a waste since they
won't actually be used by the DM device.

The passthrough keyslot manager solves this issue - when the block layer
sees that a request queue has a passthrough keyslot manager, it doesn't
attempt to program any encryption context into the keyslot manager. The
passthrough keyslot manager only allows the device to expose its inline
encryption capabilities, and a way for upper layers to evict keys if
necessary.

There also exist inline encryption hardware that can handle encryption
contexts directly, and allow users to pass them a data request along with
the encryption context (as opposed to inline encryption hardware that
require users to first program a keyslot with an encryption context, and
then require the users to pass the keyslot index with the data request).
Such devices can also make use of the passthrough keyslot manager.

Patch 2 introduces some keyslot manager functions useful for the device
mapper.

Patch 3 introduces the changes for inline encryption support for the device
mapper. A DM device only exposes the intersection of the crypto
capabilities of its underlying devices. This is so that in case a bio with

102 more quoted lines

I took care of Eric's comments.
And I already staged these changes in linux-next for dm-5.12, see:

https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-5.12

On Thu, Feb 11, 2021 at 06:04:59PM -0500, Mike Snitzer wrote:

On Thu, Feb 11 2021 at  6:01pm -0500,
Satya Tangirala [off-list ref] wrote:

quoted

On Wed, Feb 10, 2021 at 12:59:59PM -0700, Jens Axboe wrote:

quoted

On 2/10/21 12:33 PM, Mike Snitzer wrote:

quoted

On Mon, Feb 01 2021 at 12:10am -0500,
Satya Tangirala [off-list ref] wrote:

quoted

This patch series adds support for inline encryption to the device mapper.

Patch 1 introduces the "passthrough" keyslot manager.

The regular keyslot manager is designed for inline encryption hardware that
have only a small fixed number of keyslots. A DM device itself does not
actually have only a small fixed number of keyslots - it doesn't actually
have any keyslots in the first place, and programming an encryption context
into a DM device doesn't make much semantic sense. It is possible for a DM
device to set up a keyslot manager with some "sufficiently large" number of
keyslots in its request queue, so that upper layers can use the inline
encryption capabilities of the DM device's underlying devices, but the
memory being allocated for the DM device's keyslots is a waste since they
won't actually be used by the DM device.

The passthrough keyslot manager solves this issue - when the block layer
sees that a request queue has a passthrough keyslot manager, it doesn't
attempt to program any encryption context into the keyslot manager. The
passthrough keyslot manager only allows the device to expose its inline
encryption capabilities, and a way for upper layers to evict keys if
necessary.

There also exist inline encryption hardware that can handle encryption
contexts directly, and allow users to pass them a data request along with
the encryption context (as opposed to inline encryption hardware that
require users to first program a keyslot with an encryption context, and
then require the users to pass the keyslot index with the data request).
Such devices can also make use of the passthrough keyslot manager.

Patch 2 introduces some keyslot manager functions useful for the device
mapper.

111 more quoted lines

Ah, I didn't see that till a little while ago. Thanks!